The present invention relates to a seatbelt apparatus disposed at a seat of a vehicle such as an automobile for restraining and thus protecting a passenger during an emergency such as when a car crashes.
A known seatbelt apparatus is typically fixed to portions of a car body close to a car seat. The seatbelt apparatus comprises a seatbelt for restraining a passenger while he/she wears the seatbelt and which fixed to the lap belt anchor mounted on the outer side in the compartment of the car body at the end of the seatbelt, a seatbelt retractor for retracting and extracting the seatbelt during a non-emergency operation and for preventing the extraction of the seatbelt during an emergency such as when a car crashes and thus restraining and protecting the passenger, a buckle fixed to, for example, a portion of the inner side in the compartment of the car body, and a tongue which is slidably mounted on the seat belt and which can engage with the buckle. The passenger wears the seatbelt by engaging the tongue with the buckle so as to extend the seatbelt across his/her shoulder, chest, and pelvis.
While the passenger wears the seatbelt, the seatbelt retractor rolls up the seatbelt retractable and in a relatively slack manner so as to allow the seatbelt to fit to the passenger to such an extent that the passenger feels free during non-emergency operation. In addition, even though the force of inertia caused by the large deceleration of a car which takes place during an emergency such as when a car crashes pushes the passenger forward, the seatbelt retractor prevents the seatbelt from being extracted, thereby allowing the seatbelt to restrain and thus protect the passenger.
Some known seatbelt apparatuses have a pretensioner for quickly restraining the passenger with a large restraining force by tightening the seatbelt and thus improving the restraint performance of the seatbelt during an emergency such as when a car crashes. Although the pretensioners are generally disposed at the seatbelt retractor, some of the pretensioners are disposed at a portion of the car body at the inner side of the compartment in which the buckle is provided or at the lap belt anchor. An exemplary typical pretensioner disposed at the seatbelt retractor is constructed such that, during an emergency such as when a car crashes, a reactant material reacts to produce a high-pressure reactant gas, thus allowing a spool of the seatbelt retractor to rotate in the retracting direction of the seatbelt.
Also, because the passenger is subject to a large impact when a large load is exerted on the seatbelt during an emergency such as when a car crashes, some known seatbelt apparatuses have a load limiter to limit this load exerted on the seatbelt to a predetermined level. This load limiter allows the seatbelt to pay out by limiting the load to a predetermined level. Moreover, the typical load limiter is integrated into the seatbelt retractor since it is often preferable that the seatbelt securely restrains the pelvis of the passenger. The typical load limiter integrated into the seatbelt retractor has a torsion bar disposed coaxially with and extending through a center hole of the spool of the seatbelt retractor. The torsion bar is twisted by a pull-out force of the seatbelt during an emergency such as when a car crashes, allowing the load limiter to absorb shock energy during the emergency and thus to limit the load exerted on the seatbelt to a predetermined level.
Alternatively, some load limiters are disposed at the lap belt anchor. The load limiter may include a worked piece, which is connected to the lap belt anchor and which is disposed at a cylinder containing a piston. When the seat belt is withdrawn from its retracted position due to the force applied by the occupant during an emergency, the worked piece is cut by a cutting blade of the piston connected to the seatbelt, thus allowing the load limiter to absorb shock energy during the emergency which may occur when a car crashes. As a result, the load limiter limits the load exerted on the seatbelt to a predetermined level.
In recent years, a seatbelt apparatus has been required not only to merely have improved seatbelt restraint, but also to have greater technical advantages and advanced capabilities of the seatbelt for effectively restraining and thus protecting a passenger, in addition to having the improved restraint, without inflicting a large shock on the passenger owing to the increase of rigidity of a car body and the like.